For a long time, schottky diode has been an important power device featuring a metal-semiconductor junction to create a schottky barrier so as to provide the function of rectification. With the characteristics of high switching speed and rectification, the schottky diode has been widely applied to high speed switching power devices, digital computers, and output regulators
However, the present schottky diodes fabricated by using semiconductor structures has the disadvantages of low reverse breakdown voltage and large reverse leakage current. In addition, the reverse current increases with increasing temperature to result in the problem of thermal instability. Thus, schottky diode should be operated under the reverse bias much smaller than the rated value, which brings some additional limitations to the application of schottky diode.
In view of the above mentioned problem, various improvements of semiconductor structures have been developed to enhance reverse breakdown voltage and reduce leakage current, and a commonly-used improvement is to form a boron-implanted termination (BIT). The termination region is capable to moderate the electric field generated at the edge of active region under reverse bias so as to enhance reverse breakdown voltage and reduce leakage current. However, under forward bias, the output current of the semiconductor device would be restricted by the arrangement of trenches. Sometimes, a greater forward bias voltage is demanded for such semiconductor device to achieve a desired output current value, which badly influences the application thereof.
Please refer to FIG. 1, which shows a schematic view of a conventional arrangement of the active region trenches. As shown, the semiconductor structure 1 has a plurality of active region trenches 11 and an epitaxial layer 12. The active region trenches 11 has an active region dielectric layer 111 and a polysilicon layer 112 located therein, and the active region trenches 11 are of continuous stripe-shaped structures regularly arranged in the epitaxial layer 12. However, such continuous stripe-shaped structure restricts the effective usage of epitaxial layer 12 surface area and limits the output current under forward bias. Thus, in order to achieve a desired current output, a higher forward bias voltage or a larger chip size should be used, wherein the later is the method being used in the present practice to increase output current. However, neither of these methods has industrial economic efficiency.
Accordingly, it is believed that the people skilled in the art would notice that the conventional semiconductor structure has the disadvantage of low current output under forward bias, which usually needs a higher forward bias voltage to achieve the desired current output. Thus, the problem of insufficient rated output current value does exists in the conventional art.